Expansion linkage for tubular members



Dec. 21, 1954 R. G. LLOYD 2,697,420

EXPANSION LINKAGE FOR TUBULAR MEMBERS Filed July 12, 1950 3 Sheets-Sheetl f fr WIWI W :I ME

INVENTOR Russe/IG Lloyd BY www ATTORNEY Dec. 21, 1954 R. G. LLOYD2,597,420.

EXPANSION LINKAGE FOR TUBULAR MEMBERS Filed July 12, 1950 3Sheets-SheetI 2 -W- 56- 67m FIGA ha l\ S 5M 5K! INVENTOR Passe/l i/@ydBY 014ML- ATTO RNEY ec. 21, 1954 R, G. LLOYD 2,697,420

EXPANSION LINKAGE FOR TUBULAR MEMBERS Filed July 12, 1950 3 Sheets-Sheet3 46 lag" 2 7/ 4? ,'68 66 54 Il '55 44 INVENTOR /Pusse/ 61E/@yd BY ATTOR N EY EXPANSION LINKAGE Fon 'rUBULAR MEMBERS Russell G. Lloyd,Barberton, Ohio, assignor to The Babcock & Wilcox Company, Rockleigh, N.J., a corporation of New Jersey Application July 12, 1950, Serial No.173,416

3 Claims. (Cl. 122-4) The present invention relates to vapor generators,and more particularly to a thermally motivated actuator for driving atubular element in a predetermined direction and amount in response totemperature changes.

In the majority of vapor generating units, thermalsiphonic fluidcirculation through the unit is attained by a difference in thedensities in the vapor-liquid mixture in the heated leg of thethermal-Siphon, as compared with the density of the liquid in therelatively cold leg of the thermal-Siphon system. The cold leg of thesystem comprises the downcomers from the vapor-liquid drum to thereceiving ends of the heated vapor generating riser tube portion, withthe riser tube portion providing the heated leg of the system. In orderto attain maximum differentials in temperature within the riser anddowncomer portions of a thermal circulating system, the downcomer systemis customarily formed by downcomer conduits positioned out of directcontact with the heating gas stream.

With a difference in temperature between the Vapor generating portion ofthe circulating system and the downcomer portion, differentialexpansions in the connected portions result. This differential expansionis accommodated, where it is of an appreciable extent, through the useof tubular expansion bends or loops which are 'differentially movedunder operating conditions interposed between the portions. Suchmovements involve the development of stresses in the metal of thetubular expansion bends or loops. When the amount of expansion to beprovided for is unusually great and the expansion loop is heated to arelatively high temperature under operating conditions, the stressesinvolved may be higher than is considered acceptable for the highoperating metal temperatures.

This problem is accentuated in vapor generators using mercury as thefluid heat transfer medium. Mercury not only has a higher specificgravity than water but also has a boiling or saturation temperatureconsiderably higher than water at the corresponding pressure. Forexample, mercury at 140 p. s. i. has a boiling or saturation temperatureof approximately 975 F., while water at the same pressure has a boilingtemperature of approximately 350 F. The stressed expansion loops used ina mercury Vapor generator must be arranged so that the stresses in themetal of the loop tubes is within satisfactory stress limitations whenoperating at the relatively high temperatures.

While it is recognized that adequate provision for temperature expansionmay be provided by expansion tube loops having large offsets, such aninstallation would involve a considerable volume of expensive mercury aswell as additional costs from the length of tubing and the necessaryprovisions for supports and guides.

The present invention is directed to an arrangement of expansion looptubes coordinated with drive means to cause a predetermined displacementof the tubes at a position intermediate their length, whereby thestresses in the metal of the loop tubes are maintained within desiredlimits under all operating conditions while keeping the size andcharacter of the loop tubes within reasonable cost limits. The inventionis particularly directed to an expansion loop tube system in whichtheexpansion loops are displaced by forces exerted by movementsresulting from the heat expansion of a part of the vapor generator withwhich the expansion loops are associated. The invention is alsoparticularly directed to an expansion loop systemcomponent interposed inthe down- ICC -, comer portion of the circulatory system of a vaporgenerator, whereby controlled displacement ot' the expansion loops isaccomplished by the heat expansion ot' a portion of the downcomer systembefore the expansion loops attain the temperature of the expandeddowncomer portron.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart ot` this specification. For a better understanding of theinvention, its operating advantages and specic objects attained by itsuse, reference should be had to the accompanying drawings anddescriptive matter in which l have illustrated and described a preferredembodiment of my invention.

Of the drawings:

Fig. 1 is a side elevation View, in section, of a vapor generating unitincorporating the present invention;

Fig. 2 is an enlarged side elevation view of a portion of the apparatusshown in rig. l;

Fig. 3 is an enlarged end elevation View of the apparatus shown in Fig.2;

Fig. 4 is a section view taken on the line 4-4 of Fig. 2; and

Fig. 5 is a somewhat diagrammatic view of a portion of the apparatusshown in rig. 1.

The drawings illustrate the application of the invention to a vaporgenerator in which liquid mercury is vaporized to provide a hightemperature vapor uid for use in a prime mover driving an electricgenerator or for use in other heat using processes. The invention is notlimited to such installations inasmuch as it can be used to advantage inother installations where a controlled movement of one component of aunit by a change in temperature of a related component is accomplishedin accordance with a change in temperature of tne related component.

As snown in Fig. 1, the mercury vapor generator comprises a vapor andliquid drum 10, with associated mercury heating and vaporizing tubeswhich receive liquid mercury from the drum and deliver a mixture ofmercury vapor and liquid mercury to the drum. ln the vapor generatorcircuit liquid mercury flows from the drum into six downcomer conduits11 connected at longitudinally spaced positions along the bottom of thedrum. A group of three conduits is connected to a downcomer conduit 12which extends to one side of the unit and a second group is connected toa second similar downcomer conduit to the other side. Downcomer 12 andits complementary one on the opposite sid.: of the unit delivers liquidmercury through groups of expansion loops, such as 13, to bottom supplyheaders 14 for the vapor generating tubes 15 of the side walls of thefurnace 16. Expansion loops corresponding to 13, but not shown, alsoextend from downcomers 12 to the supply headers 17 and 18 from which thefront wall tubes 21 and rear wall tubes 22 of the furnace 16,respectively, receive liquid mercury.

The furnace 16 is heated by products of combustion resulting fromoperation of the low load liquid fuel burner 23 arranged in the rearwall of the furnace or by burners 24, of the pulverulent fuel type,positioned in the front wall 25.

The front wall tubes 21 extend upwardly from headers 17 forming thefront hopper wall and then vertically along the front wall to the top ofthe furnace 16 where rearward extensions thereof line the roof. From theroof level the tubes have vertical extensions 26 which are in relativelywide horizontally spaced relationship. The lower ends of the verticalextensions 26 are individually connected to U-loop tubes which arearranged as part of a horizontally extending bank, with the lowermostoutlet ends or' the individual tubes connected into the vapor space ofdrum 10. y

The rear wall tubes 22 extend from headers 18 along the rear hopper walland then vertically along the rear wall 27. The majority of tubes 22extend upwardly to a position adjacent the lower end of the verticalextensions 26 where they connect into tube lengths which are associatedas U-loop tube banks and open at their outlet ends connected into thevapor space of the drum. A portion of the tubes 22 have extensions 28 tothe uppermost level of the unit and then extend downward in a pluralityof serially'connected loops 31 to connections into the vapor space ofthe drum.

The side walls of the furnace are lined with closely spaced tubes 15,the tubes of each vwall being divided into five groups, e'aeh of 'whichreceives liquid mercury from 'a header 14. Bach group of side wall tubesis connected 'at its upper end to an outlet header 32 from whichindividual discharge connections 33 extend to the drum space.

In the vapor generating installation disclosed, theupwardly extendingheat absorbing elements, comprising the from and rear furnace wall tubes'21 and 22 and their e tensionsin the yconvection pass, are topsupported by hanger elements Serrara external structural 'stein memberssuch as 35 and` 36. The 'outlet headers 32 serving the furnace side walltubes 15 are correspondingly supported by hangers from 'superadjacentstructural 'steel members. With this arrangement, 'the 'expansion of theheat absorbing elements, upon change of temperature, will be in adownwa'rddi'rection, and in the case of a mercury vapor generator willbe 'of a substantial amount inasmuch as the temperature range will befrom atmospheric temperature up to a temperature in excess of thesaturation temperatu'r'e of the mercury, as related to Vthe pressure andthe temperature differential between the metal wall of the tube and theconfined mercury.

The drum is supported by the steel work 36 at an intermediate positionin 'the height of the unit.

Products of combustion generated in the lower part of the furnace 16from fuel and air introduced by the burners heat the exposed tubularwalls of ythe furnace in their upward travel to the furnace outlet 37from which they pass over the spaced vertical tube' extensions 2K6, andin a U-shaped path, because of bafe 38 associated with tube extension 28over, the horizontally extending banks and themultiple loops 31, to agas outlet 41.

The mercury in the front, rear and side Walls is heated and caused tocirculatedue to the thermosyphonic action, delivering a vapor-liquidmixture of high quality to the drum 1t). Unvaporized liquid is separatedwithin the drum and ows by gravity into the conduits 11, while theseparated vapor is delivered through outlet 42 to a mercury turbine orother user. A feed of liquid mercury to replace that passing from thedrum 10 is .provided by conduit 43 which receives its `supply from thecondenser or some similar source of liquid mercury.

The invention, as applied to the above described mercury vaporgenerator, -is utilized in providing a thermally actuated device inconjunction with the expansion loops interposed in thedowncomer portionof the circulatory system, so that adequate provision will be made forthe differential expansion incurred without subjecting the metal of theloops to unacceptable stress conditions when hot, yet retaining aneconomical design as regards the utilization of expansion loops land arelatively small volume of mercury charge.

The downcomer system between the drum and the lower supply headers ofthe furnace wall tubes is shown in detail in Figs. 2, 3 and `4, andcomprises a pair of downcomers 12, of which one only is shown in thedrawings, and the description will be limited to one. The down comer 12extends horizontally with a slight downward inclination alongside theoutside of the unit from the rear to a central position relative to theside ofthe unit, and between that position and a vertically dependingportion is provided with a bend 44. The downcomer 12 is provided withthree points of support and guidance by a resilient spring hanger 45adjacent the rear corner of the unit, a vertical loading attachment by adrive member 46 and a parallelogram guide 47 to the vertical dependingportion.

The vertically depending conduit portion below the guide 47 includes amanifold section 4S with a plurality of longitudinally spaced integraltube stubs 51 for field attachment by welding to the supply ends of theexpansion loops 13 as indicated at 52. The upper end of the manifoldsection 48 has a field weld attachment as indicated at 53 connecting itto the vertical conduit portion depending from drive member 46. Withcompletion of the aforementioned welds a liquid mercury ow path isprovided vfrom the drum 10 to the lower supply headers 14, 17 and 18 ofthe furnace wall tubes.

As illustrated by Figs. 1, v2, 3 and 4, a linkagearm 49 of the drivemember 46 is attached to the bend 44 of downcomer 1'2 by a pin 54extending between a pair of plate lugs attached by welding to the arc ofthe bendv 44. The upper end of the linkage arm 49 has an attachment bypin 56 to a horizontally extending arm 57 of a bell crank which isprovided with a pin type fulcrum at 58 and has a depending arm 61.

The thermally motivated actuator or drive member 46, for modifying theposition of bell crank mounted pin 54 is made up of the hereafterrelated elements.

The pin type fulcrum 58 is carried by a xed bracket 62 attached to thestructural steel member 63. The depending arm 61 is attached by pin 64and bolted bracket 65 to a tie member 66 which is built up of steelmembers and extends substantially parallel to the horizontally inclinedsection of downcomer 12. The member 66 is attached at a position spacedfrom pin connection 64 to opposite sides of a collar 67 encircling thedowncomer conduit 12 and rigidly fixed thereon. A shim plate 68 ofselected thickness is interposed between the bracket 65 and the tiemember 66 as a means of adjusting the dimension A between pin S4 and thecollar 67.

A guide link 71 extends between the pin connections 54 in the lugs 55 toa pin connection 72 in a fixed structural steel member 73, permittingthe pin 54 to move through a relatively fiat vertical arc. This servesas a relatively simple guide for movement of the bend 44 of thedowncomer 12.

In the assembly of the downcomer conduit parts with the associatedexpansion loops 13 attached to the lower headers 14, 1'7 and 18, thelength of the depending manifold section 48 of the downcomer below theweld 53 is made of a dimension that it must be moved downward in orderto bring the related conduit ends in juxtaposition to complete the weldS3. With the previous connection of expansion loops 13 to the manifoldsection by welds 52, such a downward movement distorts the expansionloops, tending to close them. This places the metal of the expansionloops under a prestressed condition upon initial assembly. v

The parallelogram guide 47 as shown in the drawings has two collars 74and 75 at longitudinally spaced positions on the depending manifoldsection 48 of the downcomer conduit. These collars each have pinattachments 76 to corresponding ends of a pair of guide links 77, whichare attached by pins 78 to brackets 81 fixed to a stationary structuralmember 82. The links are of the same lengths between pins, and the pins76 are the same distance apart as pins 78, so that with any up or downmovement of the collar embraced section, it is kept in parallelism asregards its previous positions. The combination of guide link 71 and theparallelogram guide 47 insure a controlled positioning of the dependingsection of the downcomer 12 irrespective of any vertical movement causedby the drive member 46. Y

In the normal operation of the mercury vapor generator described, themercury level is maintained between the bottom ofthe drum 10 and theelevation at which the conduits 11 are attached to the inlet end portionof the downcomer conduit 12. .Even though the mercury level may, underabnormal conditions, attain an elevation within the drum 10, the levelof the mercury is aiways considerably below the top or discharge end ofthe furnace Wall tubes 15, 21 and 22. With such a level relationship,

circulatin does not take place within the vapor generator until asufficient proportion of the mercury in the tubes is vaporized so thatthe vaporliquid mixture discharges through the convection heated tubeextensions 26 or 23 or the side wall discharge connections 33 to thedrum 10.

During the period of time when the change of density is beingaccomplished by the initial burning of fuel, the wall tubes are heatedup and expand downwardly from their top supports. This expansion movesheaders 14, 17 and 18 downward, and this movement tends to open theexpansion loops 13, inasmuch as the manifold sec tion '48 does not move.This opening of the loops modilies the stresses in the loop tubes aspreviously imposed in the initial prestressing during assembly, asbefore dcs'cribed, by imposing opposite stresses due to the .greatextent of the downward movement of the lower headers. The oppositestress inducing movement is of such magnitude as to have this reversedstress minimized upon subsequent downward thermal expansion of theheader 12,

manifold 48 and lloops 13 by rising temperature of the mercury tiowingtherein.

While the stresses so developed in the metal of the expansion loops 13under starting conditions, wherein the wall tubes are expanded and thedowncomer is relatively cold due to absence of circulation, may be of anacceptable value while the expansion loop tubes are relatively cold, thestresses would be too high for normal operating conditions when liquidmercury at a relatively high temperature flows through the tubularloops.

A downward flow of relatively cold mercury in the downcomer portion ofthe system is initiated upon discharge of a mixture of vapor and liquidto the drum from the furnace heat absorbing tubes. The vapor portion ofthe mixture is separated from the liquid portion and delivered to pointof use, while the separated liquid and a feed of liquid mercury from anexternal source passes into the downcomer system. This mercury liquid isat a relatively high temperature.

As the ow through the downcomer proceeds with the continued generationof vapor, the hot mercury liquid will reach the inclined portion of theconduit 12 at collar 67. As the zone of hot liquid advances from thecollar toward the bend 44, the liquid will heat up the metal of theconduit from its initial relatively cold temperature to closely approachthe temperature of the liquid, inasmuch as the conduit 12 is suitablycovered with heat insulation. The change of temperature causes anexpansion and elongation of the heated zone of the conduit so thatpoints on the conduit as measured by dimension A under cold conditionsare moved further apart, when heated. As the drive member 46 is notsubject to a corresponding temperature change, a compensating increasein the dimension B between the pin 56 and collar 67 is accomplished by acounter-clockwise rotation of the drive member about its fulcrum pin 58.Counter-clockwise rotation of the drive member moves the pin 54 downwardlowering the manifold section 48 and reducing the stresses in theexpansion loops 13 as incurred from the previous downward movement ofheaders 14, 17 and 18. As the hot liquid progressively flows downwardfrom the bend 44 to the lower end of the depending manifold section 48 afurther downward stress modifying movement results from the elongationof the section due to its rise in temperature. Thus, the subsequententrance of hot liquid mercury into the expansion loops 13 has beenanticipated by the movement of the manifold section 48 to reduce thestresses in the loops to a value which is acceptable for hightemperature operation.

With the described arrangement of a combination of a thermally actuateddrive member and a prestressed assembly of the expansion loops when inan unheated condition, the overall range of loop displacement isincurred with tube metal bending stresses changing from a minus value atone extreme to a plus value at the other extreme of movement, withmaximum stress values of a character which are but a fraction of thevalues incurred if such stresses were solely minus or solely plus incharacter.

While other expedients, as for example by an increase in the tube wallthickness, might be used to obtain a stress condition in the expansionloop tubes which would be satisfactory for the relatively hightemperature operating condition, the decrease in exibility of thickertubes requires an increase in the offset dimension of the loops andinvolves higher costs due not only to higher material and fabricationcosts, but also because of the increased weight of costly mercury tolill the additional expansion tube volume.

It will be apparent that the movement developed by the thermallyactuated drive mechanism of the invention may be directed in an upwarddirection, if such a direction oi' the developed thrust is indicated.The drive mechanism of the invention is also applicable to the movementof tubular expansion bends or loops handling high temperature uids otherthan heated mercury, and in applications other than in the circulatorysystem of a vapor generator.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

I claim:

1. ln a vapor generator having a top supported vapor generating tubeopening to a lower header and to an upa substantially upright lower endportion ending adjacent said lower header, a exible tubular expansionloop con-'- necting sald downcomer conduit and said header, and.

thermally motivated means operative to regulate downward movement of thesubstantially upright lower end portion of said downcomer conduit inresponse to temperature changes within another portion of said downcomerconduit.

2. In a vapor generator having a top supported vapor generating tubeopening to a lower header and to an upper liquid supply drum, thecombination comprising a downcomer conduit connected with said drum andhaving a horizontally inclined portion and an upright lower end portionending adjacent said lower header, a flexible uid supply tube connectingsaid downcomer conduit and said header, and means motivated by thermalchanges in the horizontally inclined portion of said conduit to directand control downward movement of the upright lower end of said downcomerconduit.

3. In a vapor generator having top supported vapor generating tubesopening to lower headers and to a liquid supply drum supported at alevel intermediate the height of said tubes, the combination comprisinga downcomer conduit connected with said drum and having a substantiallyupright lower end portion ending adjacent said lower headers, aplurality of prestressed exible tubes connecting said downcomer conduitand said headers, the fabricated straight line distance between ends ofeach of said flexible tubes having a selected vertical dimension greaterthan the vertical spacing between the header and conduit connections ofeach tube when cold, and a thermally motivated mechanism including a xedposition fulcrum, and a bell crank pivotably connected with said fulcrumand a linkage connected to said bell crank andV at spaced positions onsaid downcomer conduit to position the lower portion of the downcomerconduit downwardly in response to temperature changes in the portion ofsaid conduit between the spaced positions of said mechanism.

4. Apparatus for controlling the thermal movement of an elongatedtubular element in response to changes in the temperature of theelement, said apparatus comprising a collar attached to said element, alug longitudinally spaced .from said collar and attachedlto saidelement, a tie member attached to said collar at one end of the tiemember and having an arm portion of the tie member extending generallyparallel to said element toward said lug, a pivot pin rigidly supportedat a position spaced from said elongated element, a bell crank having adepending arm pivotably connected with said tie member and pivotablyattached to said supported pivot pin, and a linkage arm pivotablymounted at its opposite ends to said bell crank and said lug.

5. Apparatus for controlling the thermal movement of an elongatedtubular element having a bend intermediate its length, said apparatuscomprising a collar attached to said element, a lug longitudinallyspaced from said collar and attached to said element at said bend, amember attached to said collar at one end of the tie member and havingan arm portion of the tie member extending generally parallel to saidelement toward said lug, a fulcrum pin supported at a position spacedfrom said elongated element, a lever arm pivotably connected with saidmember and pivotably attached to said fulcrum pin, and a linkage armpivotably connected at its opposite ends to said lever arm and said lugand substantially in alignment with the longitudinal axis of the portionof said element extending beyond said bend remote from said collar andlug.

6. Apparatus for controlling the thermal movement of an elongatedtubular element in response to changes in the temperature of saidelement, said apparatus comprising a fixed fulcrum spaced from saidelement, a bell crank attached to said fulcrum, a member pivotablyattached to a depending arm of said bell crank and its opposite endattached to said elongated tubular element, and a linkage arm having oneend pivotably attached to the other arm of said bell crank and dependingtherefrom with the lower end of said linkage arm pivotably connectedwith said tubular element at a position longitudinally spaced from thepoint of attachment of said member and said tubular element, whereby tourge said tubular element downwardly at said position.

7. In a lluid ow system, the combination comprising an inletand anoutlet conduit, Va plurality of flexible tubular expansion loopsarranged in parallel with each ,other and .connecting the end portionkof `said inlet conduit with the outlet conduits for iluid owrespectively therethrough, heating means causing downward .movement ,ofsaid outlet conduit in response to a temperature change within saidconduit, and a driving mechanism including .a fixed fulcrum positionedexternally of said inlet conduit, a bell vcrank associated with saidfulcrurn and attached by connecting linkage to spaced positions alongand motivated by temperature change within :said inlet conduit causingmovement of the expansion loop end portion of said inlet conduit.

8. Apparatus for controlling the thermal movement yof an elongatedtubular element having ia bend intermediate its length comprising acollar attached to said element, a lug longitudinally spaced from saidcollar and attached ,to said element .at said bend, a member attached tosaid collar at Vone end and having .an arm portion extending generallyparallel to vsaid element toward said lug, a fulcrum pin rigidlysupported at a position vspaced from said kelongated element, a leverarm pivotally connected with said member and pivotally attached to saidYfulcrurn pin, a linkage arm pivotally connected at its oppositej endsto `said lever arm and said lug and substantially in alignment with ltheaxis of the portion of said tubular element beyond said bend remote fromsaid collar andl lug, a guide link arranged to guide the movement ofsaid bend n a at arc lying in a plane common with the longitudinal axisof said tubular element, and a parallelogram guide attached to saidtubular element at a position spaced from said collar and said lug torestrain thc movement of said tubular element within the plane of saiddat arc.

References Cited in the le of this patent UNITED STATES PATENTS

